由陆地人类活动排放的污染物通过降雨径流进入水体，污染物从河流入河口后，生物地球化学条件变化剧烈，污染物以及主要离子之间原有平衡关系被打破，在河口海岸带形成新的平衡，随后进入海湾地区。海湾地区介质复杂，半封闭性海湾使得污染物在湾区内有更长时间进行迁移分解过程，造成了污染物在湾区内的复杂环境行为。农药由陆地向河流运输主要受使用规模以及降雨驱动，二者均具有强烈的季节变化，导致不同季节农药污染风险不同，因而对农药的季节性监测具有必要性。阿特拉津作为毒性较强、半衰期较长的农药，已经被列为优先污染物，为评估其环境风险，阿特拉津在环境中的归趋行为至关重要。

基于以上背景，本研究选取我国典型半封闭型海湾—山东省胶州湾为研究区，分析大沽河流域主要河流不同介质中阿特拉津的沿程变化规律，建立SWAT模型，估算不同季节大沽河流域阿特拉津流失量，并基于室内实验，分析河口及海湾地区阿特拉津及其降解产物在水体、悬浮颗粒物和表层沉积物中的时空变化特征，探究不同季节阿特拉津降解特征，以及不同物质相分配的季节变化特征，揭示影响湾区阿特拉津浓度变化的主要环境因子。主要结论如下：

（1）大沽河流域主要河流水体中从上游到下游阿特拉津浓度逐渐增大，表明沿程一直有阿特拉津不断输入，且阿特拉津更倾向于在溶解态中进行迁移。SWAT模型表明，阿特拉津流失量整体呈现波动中下降规律，在6~8月流失量达到峰值，流域中部以及河口西部区域为流失关键区，从空间分布来看，夏季流失量增加且具有明显的空间分布差异。夏季流失量高与阿特拉津的施用时间有关。

（2）水体中阿特拉津浓度整体呈现河口>海湾的规律，海水稀释导致浓度下降，同时表明河口具有一定的缓冲作用。洋河与大沽河是该地区污染风险较高的河流。夏季西部河流中阿特拉津的浓度明显高于东部河流，这与土地利用类型有关，大沽河与洋河主要为耕地，施用阿特拉津较多，而东部地区城市用地面积大。不同地区悬浮颗粒物中阿特拉津浓度相差不大。湾区颗粒物中污染物分布与河口输入分布较为相似，表明河口地区污染物是海湾的主要输入源。夏季降水携带更多土壤颗粒进入河流，造成河口沉积物中阿特拉津浓度随季节变化浓度升高。表层沉积物中阿特拉津在湾内呈现湾中心浓度低，沿岸浓度高的特点，这与湾内沉积物的斑状分布有关，黄岛北部粘粒组分含量高，加剧沉积物的吸附过程。

（3）水体中HyA浓度随季节变化逐渐降低，表明阿特拉津水解速率逐渐降低。冬季和夏季DIA空间分布差异较大，表明脱异丙基过程受到环境影响较大。DEA和DIA在湾区北部呈现带状分布，与东西方向的余流有关；HyA则受湾中心涡流影响。降解产物在湾区的空间分布也表征了湾区内不同地区、不同季节降解过程的差异性。河口地区冬、春季悬浮颗粒物中DDA空间分布差异较大，夏季HyA与DIHA差异较大，表明前两个季节阿特拉津完成次级降解后，由于再次施用阿特拉津而发生初级降解，这与水体规律类似。同一季节不同降解产物在悬浮颗粒物中空间分布状况较为接近，表明颗粒物中降解产物的空间分布与湾区内余流的季节变化有关。大沽河及洋河河口表层沉积物中阿特拉津均处于次级降解过程，DDA含量不断累积。湾区内沉积物中初级降解产物高浓度值均分布于沿岸区域，一方面与陆地相接，一方面岸边水体交换能力弱，来自陆地的污染物扩散能力较弱，易于在此积累。

（4）阿特拉津在不同介质中均发生了降解过程，且以次级降解过程为主。除DDA外，其余物质在夏季更易于吸附在颗粒物上，影响水-颗粒物分配过程的主要环境因子是水中颗粒物含量。逸度分数值表明沉积物是DEA、DEHA、DIHA和DDA的二次释放源，且季节性变化与沉积物含水率相关。溶解氧、温度以及盐度是海水中阿特拉津浓度变化的主要因子，pH、含水率则是影响沉积物中阿特拉津浓度变化的主要因子。

Pollutants discharged by human activities on land enter water body through rainfall and runoff. After entering estuaries, the biogeochemical conditions change dramatically, the original balance between pollutants and major ions is broken, forming a new balance in estuaries and coastal zones, and then entering into the bay. The media in the bay area is complex, and the semi-closed bay allows the pollutants to migrate and decompose for a longer time, resulting in complex environmental behavior of pollutants in the bay. The transport of pesticides from land to rivers is mainly driven by the use scale and rainfall, both of which have strong seasonal changes, leading to different pesticide pollution risks in different seasons. Therefore, it is necessary to carry out seasonal monitoring of pesticides. As the strong toxicity and long half-life, atrazine has been listed as a priority pollutant. In order to evaluate its ecological risk, the trend behavior of atrazine in the environment is very important.

Based on the background, this study selected Jiaozhou Bay, a typical semi-closed bay in China, as the study area, analyzed the variation pattern of atrazine in different media of major rivers, established SWAT model, estimated the amount of atrazine in the Dagu River Basin in different seasons. Based on laboratory experiments, the spatiotemporal variation characteristics of atrazine in water, suspended particulate matter(SPS) and surface sediments in estuary and bay were analyzed, and the migration characteristics of atrazine in different media were obtained. At the same time, spatiotemporal variation characteristics of atrazine degradation products in different media were explored to reveal degradation process of atrazine in the bay and its influencing factors. Main conclusions are as follows:

(1) The concentration of atrazine in main rivers of Dagu River Basin increased gradually from the upstream to downstream, indicating that atrazine had been continuously input along the river. Atrazine is more likely to migrate in dissolved state. SWAT model showed that the atrazine loss decreased in fluctuation, and the loss reached the peak in June to August. The central part of the river basin and the western estuary area were the key areas of loss. From the perspective of spatial distribution, the loss increased in spring and summer with obvious spatial distribution differences. The high load loss in summer was related to the application time of atrazine.

(2) The ecological risk of Yang River and Dagu River were higher. In summer, atrazine concentration in western rivers was significantly higher than that in eastern rivers, which was related to landuse types. Dagu River and Yang River were mainly cultivated land, while the urban area was large in west part. There was no significant difference in atrazine concentration in SPS between estuary and bay. Distribution of pollutants in the bay is similar to that in the estuary, indicating that pollutants in the estuary are main input source of bay.Precipitation in summer brought more soil particles into river, causing atrazine concentration in estuarine sediments to increase with the change of season.In the surface sediments of the bay, the concentration of atrazine was low in the center of the bay and high along the Bay, which was related to the porphyry distribution of sediments in the bay. The high content of clay components in north of Huangdao intensified the adsorption process of sediments.

(3) The concentration of HyA in water decreased with the seasonal change, indicating hydrolysis rate of atrazine decreased. There was a significant difference in the spatial distribution of DIA in winter and summer, indicating deisopropyl process was greatly affected by environment. DEA and DIA show a zonal distribution in the north of the bay, which is related to the east-west residual current. HyA is affected by the bay Central Vortex. Spatial distribution of degradation products in the bay also indicated the difference of degradation processes in different regions and seasons. Spatial distribution of DDA in SPS in estuary was significantly different in winter and spring, and there was a significant difference between HyA and DIHA in summer, indicating that primary degradation occurred due to the reapplication of atlazine after the secondary degradation in the first two seasons, which was similar to the law of water body. In the same season, the spatial distribution of different degradation products in SPS was similar, indicating that the spatial distribution of degradation products in particulate matter was related to the seasonal variation of residual current in the bay.The higher concentration of organic particles near the bay mouth in summer is the reason for the higher concentration of some pollutants in the bay mouth.Due to the different surrounding environment, the degradation rate of pollutants in surface sediments is different in different estuaries. Dagu River and Yang River are all in the secondary degradation process, and DDA keeps accumulating. High concentration of primary degradation products in the sediments of bay is evenly distributed in the coastal area. On one hand, it is connected with land, on the other hand, the exchange capacity of coastal water is weak, so it’s easy to accumulate.

 (4) Atrazine degradation occurred in different media, and the secondary degradation was the main process. Except DDA, other substances are more easily adsorbed on particulate matter in summer. Main environmental factor affecting the water-particulate matter distribution process is the content of particulate matter. ff value shows that sediment is the secondary release source of DEA, DEHA, DIHA and DDA, and seasonal variation is related to sediment water content. Dissolved oxygen, temperature and salinity are main factors affecting atrazine concentration variation in seawater. pH, organic matter content and water content are main factors affecting change of atrazine concentration in sediments.